Process for the liquid ammonia treatment of yarns

ABSTRACT

Yarns with improved strength, luster, elongation, and toughness are produced by a rapid and continuous process wherein singles and plied yarns which contain about 25 percent or more cotton are stretched before, during, and after immersion in liquid ammonia.

United States Patent 1 Calamari, Jr. et al.

[ 1 Oct. 23, 1973 PROCESS FOR THE LIQUID AMMONIA TREATMENT OF YARNS [75] Inventors: Timothy A. Calamari, Jr.; Wilson A. Reeves; Sidney P. Schreiber; Albert S. Cooper, Jr., all of Matairie, La.

[73] Assignee: The United States of America as represented by the Secretary of Agriculture, Washington, DC.

[22] Filed: May 7, 1971 [21] Appl. No.: 141,360

[52] US. Cl 8/1l5.7, 8/125, 8/181, 28/76 R, 8/DIG. 4, 8/DIG. 21

[51] Int. Cl. D06m l/l0, D06m 9/04 [58] Field of Search 8/125,115], 116.2, 8/181 Primary ExaminerGeorge F. Lesmes Assistant Examiner-J. Cannon AttorneyR. Hoffman and W. Bier [57] ABSTRACT Yarns with improved strength, luster, elongation, and toughness are produced by a rapid and continuous process wherein singles and plied yarns which contain about 25 percent or more cotton are stretched before, during, and after immersion in liquid ammonia.

6 Claims, N0 Drawings PROCESS FOR THE LIQUID AMMONIA TREATMENT OF YARNS A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to a process for the liquid ammonia treatment of yarn composed of either cotton or cotton and synthetic fibers. More specifically, it deals with a rapid process for the continuous tension mercerization of cotton and cotton/synthetic yarns with liquid ammonia or ammonia solutions of primary amines, which impart a combination of improved strength, luster, and elongation without imparting an increase in dye substantivity.

ln copending application Ser. No. 141,353, filed of even date, a device is disclosed which has utility in the treatment of yarn, and fabrics with liquid ammonia.

In copending application Ser. No. 141,359, filed of even date, a process is disclosed for the continuous treatment of woven and knitted fabrics with liquid ammonia to improve the physical properties of fabrics.

Heretofore it was known that treatment of cotton yarns with liquid ammonia improves strength and luster. Special processes and equipment for treating yarn which impart increased strength and luster, and reduced extensibility are available. Such a process consists of treating a relaxed yarn with liquid ammonia, then subjecting it to an ammonia-removing treatment. During the ammonia-removing treatment only, the yarn is stretched. This causes an elongation of the yarn of between and 30 percent. Although an ammonia treatment requires much less time than a conventional sodium hydroxide-treatment to produce equivalent or better results, current processes do nottake full advantage of the rapid nature of ammonia mercerization. (When such processes are made vary rapid, and/or the equipment made more compact, considerable force is applied abruptly to the yarn during the ammoniaremoving treatment causing processing difficulties-- -particularly the breaking of yarns.)

We have nowfound that improved strength and luster of ammonia treated yarns are brought about largely by changes in the surface of the fiber. Reduced extensibility is brought about largely through internal changes in the. fiber. To bring about the internal changes in the fiber it is necessary for the ammonia to thoroughly pen etrate and swell the fiber. Ammonia penetrates a relaxed' yarn much more thoroughly and rapidly than it does a tensioned yarn. In the present process, yarns are tensioned and stretched before, during, and after immersion in liquid ammonia. The. stretching is progressively and uniformly increased from a point just preceding immersion in ammonia to a point where the yarn contains not more than about 10 percent by weight of ammonia. Furthermore, we have found that stretching the yarn prior to immersion in liquid ammonia as well as during and after immersion produces yarn with greater elongation at the breaking load than exhibited by untreated control yarn. The amount of stretch prior to immersion in ammonia needed to produce this increased elongation is from about one to'five percent. The total amount of stretch during the overall process required for optimum results in the treated yarn is dependentupon the composition and construction of the yarn being processed. Singles yarn should not be stretched substantially beyond 15 percent, but must be stretched at least about five percent. Plied yarn must not be stretched substantially beyond 25 percent, but must be stretched at least about five percent. The immersion time is from about 0.1 seconds to 4 seconds. The total processing time is from about 1 to 10 seconds.

More specifically the products and processes of this invention may be described as follows: One or more singles or plied yarns, such as a sheet of yarns, are tensioned sufficient to elongate each yarn from about one to five percent, then the yarns are immersed in liquid ammonia from about 0.1 to 4 seconds while progressively and uniformly being stretched. Finally, while the yarns are still being tensioned and stretched the ammonia is removed.

Yarns suitable'for use in this invention contain about 25 percent or more cotton. Other fibers which may be contained in the yarns include polyester, polyamide, glass, rayon, acrylic and'oth er fibers which are substantially unaffected adversely by the ammonia treatment. The fibers within the yarn may be either an intimate blend or plied yarns in which one strand may be cotton and the other one of the synthetic fibers listed above.

Yarns processed in accordance with this invention exhibit improved strength, luster, and elongation compared to untreated yarn. Since toughness may be defined as one-half the product of the strength times the elongation, it follows that improved toughness is always observed for yarns processed as outlined above. This is a particularly important aspect of this invention. Either before or after crosslinking treatments, both knit and woven goods made from yarn treated in accordance with this invention exhibit greater breaking strength, tearing strength, abrasion resistance, and a higher ratio of dry to wet wrinkle recovery than similar fabrics made'from untreated yarn.

EXAMPLE 1 This example illustrates the continuous tension mercerization of cottonyarn with liquid ammonia. The yarn used in the work was a loose twist greige 10/2 Deltapine cotton yarn having a T.M. of 2.21(6.99 tpi.) in the singles with a reverse ply T.M. of 3.11( 6.95 tpi.). A sheet of three jends was batched on a skein winder and fed into an improved chainless mercerizer which subjected the yarn to a constantly increasing tension. The yarnswere elongated about two-percent by the time they were immersed in the cold (about -35 C) liquid ammonia. In this example merceri zation was terminated by induced evaporation of ammonia from the yarn by means of two 150 watt infrared lamps. Immersion time in the liquid ammonia was about'0.4 sec.

Evaporation was induced beginning'2.5 see. after the initial immersion, and was over percent complete 5 sec. later. Some physical properties of the ammonia mercerized yarn are given below in Table 1.

TABLE 1 Tena- Elon- Breaking city gation Toughness Strength (g/tex) to (B.S.XElong)/2 (8) Break Control (IO/2 yam) l274 10.8 7.7 4905 Liquid NH; for 5 see. 1524 12.6 8.2 6250 Ammonia removed by heat induced evaporation.

As can be seen from the data given above substantial increases in yarn breaking strength, tenacity, elongation, or toughness can be obtained using this new procedure. Yarn length was increased 18.6 percent by the treatment.

EXAMPLE 2 TABLE 2 Tena- Elon- Breaking city gation Toughness Strength (g/tex) to (B.S.XElong)/2 (g) break Control (40/2 yarn) I07 I 1.1 6.2 332 Liquid NH for 8 sec. 130 13.7 7.2 468 Ammonia removed by quenching with hot water.

The data in Table 2 again indicate a significant increase in yarn breaking strength, tenacity, elongation and toughness when an ammonia mercerized sample is compared to an untreated control. Yarn length was increased 12.6 percent by this treatment.

We claim:

1. A rapid and continuous process of treating yarn containing at least about 25 percent cotton to improve its strength, luster, elongation, and toughness without imparting an increase in dye substantivity, comprising tensioning the yarn to elongate it about from 1 to 5 percent, immersing the thus-elongated yarn in liquid ammonia for about from 0.1 to 4 secondswhile subjecting the yarn to progressively and uniformly increased stretching and, within 10 seconds from the time of immersion, removing about percent of the ammonia from the yarn while subjecting the yarn to progressively and uniformly increased stretching so that at the end of this time the yarn will have undergone a total elongation of about from 5 to 25 percent during the ammonia treatment.

2. The process of claim 1 wherein the yarn consists of cotton.

3. The process of claim 1 wherein the yarn consists of about 50 percent cotton and about 50 percent polyester fiber.

4. The product produced by the process of claim 1.

5. The product produced by the process of claim 2.

6. The product produced by the process of claim 3. 

2. The process of claim 1 wherein the yarn consists of cotton.
 3. The process of claim 1 wherein the yarn consists of about 50 percent cotton and about 50 percent polyester fiber.
 4. The product produced by the process of claim
 1. 5. The product produced by the process of claim
 2. 6. The product produced by the process of claim
 3. 